(Not Applicable)
(Not Applicable)
The present invention relates generally to heel grounders, and more particularly to an improved heel grounding device which allows its wearer to visually check for proper dissipation of electrical voltages to ground simply by observing the fasteners such as rivets holding the assembly of parts together remain intact.
In the assembly of electronic components, a major threat to the quality of such assemblies is the electrical potential difference existing between the electrical part assembly and the operator which may cause the part to be damaged. The typical solution to this electrostatic discharge problem in the work place has been to provide an environment which is substantially at a zero electrical potential. Electrostatic-free environments are typically created by providing workers and work stations with anti-static carpets, conductive or dissipative grounded desk top work surfaces, and/or hot air ion generators which emit ions to neutralize static charges.
Although such environments have proved to be generally useful in alleviating the electrostatic discharge problem, they do not typically have the degree of effectiveness that is desired by the manufacturers. Specifically, electrostatic-free environments fail to directly ground the workers themselves to a zero electrical potential. In this regard, electrically conductive bracelets have been implemented within such environments to sustain the workers at the zero electrical potential. However, these bracelets suffer from the disadvantage of limiting worker movement between work stations.
As such, various footwear grounding devices have been developed which can conduct electrical charges to ground while allowing the workers substantially unlimited mobility throughout the work place. A typical footwear is a heel grounder which is generally formed of a conductive rubber band and an elastic counter band or garter band. The prior art heel grounder further includes a fabric grounding tab generally of a woven polyester material coated with a conductive elastomer (such as neoprene loaded with 30% carbon), or alternatively metallic thread (such as silver yarn) is interwoven into the fabric of the grounding tab. It also includes a plastic fastening strap typically having a hoop and loop fastener, as well as a one-meg ohm chip resistor for providing additional safety of the worker against electric shock.
Though such currently known and available heel grounders may achieve their primary objective of properly grounding the workers, they possess certain deficiencies which detract from their overall utility. Perhaps the greatest deficiency of the prior art heel grounders lies in the method of their construction.
In the existing construction, the biggest problem is that all parts such as conductive rubber band and garter band are integrated and sewn together. In other words, all the parts forming the heel grounder are sewn and hidden among each other. However, if the sewing thread becomes loose and broken during use, then electrical continuity between the parts also become broken. Such occurrence inevitably leads to the undesired effect of destroying the conduction of electrical charges between the worker and earth ground.
The parts of the heel grounder need not come apart fully in order to destroy the charge conduction as loosening of the threads is generally sufficient to break continuity. This is where most of the electronic components are damaged. If the parts do not fall apart from each other, there is no way for the worker to know there is a problem unless the heel grounder is checked using a heel grounder tester. This is not practical and generally not done especially when the worker is in the middle of assembly. Hence, various electronic components become unintentionally damaged no matter how much effort was expended in providing a electrostatic-free environment.
Thus, there exists a substantial need in the industry, and in the microelectronics business in particular, for a heel grounding device that enables workers to quickly and accurately check for proper dissipation of electrical voltages irrespective of the work stage they are in. More specifically, there exists a need for a visually apparent heel grounding device which allows the workers to easily and rapidly visually check for proper electrical condition in a user-friendly manner.
The present invention specifically addresses and alleviates the above-referenced deficiencies associated with the use of the heel grounders of the prior art. More particularly, the present invention comprises an improved heel grounding device which allows its wearer to quickly, visually check for proper dissipation of electrical voltages to the earth ground. As will become more apparent below, this is accomplished by visually verifying that the assembly of parts forming the present heel grounding device through the use of fasteners such as rivets remains intact.
In accordance with a preferred embodiment of the present invention, there is provided a grounding device which can be worn around a shoe in order to dissipate electrical voltages from the wearer to the earth ground. The heel grounding device of the present invention preferably utilizes two plastic anchor plates which are adapted to be maintained on opposing side portions of the wearer""s shoe. An elongate electrically conductive strap preferably fabricated from rubber is formed between the anchor plates and is designed to extend around the heel portion of the wearer""s shoe. Such conductive strap is preferably riveted to the plastic anchor plates.
In the preferred embodiment of the present invention, the heel grounding device also features an elongate garter strap or band which is formed between the two plastic anchor plates. The garter strap helps to secure the grounding device to the wearer""s shoe by extending around its rear portion. Preferably, the garter strap is fabricated from an elastic material.
An attachable/detachable hook-and-loop (Velcro.TM.) system is further defined between the two anchor plates to provide adjustable fastening of the grounding device to the wearer""s shoe. Such system is comprised of a hook strip and a loop strip which extend outwardly from their respective anchor plates and are releasibly connected to each other around the upper portion of the wearer""s shoe. As is well known, the hook strip""s inner surface may be connected at any location along the outer surface of the loop strip in order to provide adjustable fastening.
In the preferred embodiment, a grounding tab is riveted to any one of the two plastic anchor plates and extends freely (i.e. dangles) therefrom. The exposed end of this tab maybe tucked inside the wearer""s sock so as to touch his or her skin. The grounding tab is preferably made from fabric such as polyester which includes either are electrically conductive elastomer or metallic thread.
A chip resistor which is preferably used for preventing electric shocks which preferably is provided on the same plastic anchor plate that the grounding tab extends from. This chip resistor is formed between the points of rivet attachment of the conductive strap and the grounding tab as the same rivets are used to mount the resistor on the anchor plate. The chip resistor preferably comprises a one-meg ohm chip resistor.
In operation, the heel grounding device of the present invention is worn around the wearer""s shoe by first placing the shoe""s heel portion upon the elongate conductive strap. Thereafter, the shoe""s rear portion should be closely abutted against the garter strap or band so that tensioning fit develops once the grounding device is fastened. The hook and loop strips are then extended around the shoe""s upper portion and fastened, after which the grounding tab""s exposed end is tucked inside the wearer""s sock so as to touch his or her skin. Of course, the strips may be adjusted to accommodate differing sizes and styles of the shoes.
With the heel grounding device on, the wearer is effectively grounded to zero electrical potential. Hence, the wearer may stand or freely walk on the grounded conductive surface while performing his or her electronics assembling duties. Thus, there is no unintentional static discharge to the electronic components to cause damage.
Due to all of the electrical connections to the heal grounder being facilitated by the conductive rivets attached to the anchor plates which can be easily visually observed by a user during use the user can easily check for proper dissipation of electrical voltages simply by observing the rivets holding the assembly together remain intact. As such the present invention comprises a visually apparent/evident heel grounder which insures proper electrical grounding merely by quick visual observation of the rivets and on anchor plates.